Characterization and amino acid sequence of the OXY-2 group beta-lactamase of pI 5.7 isolated from aztreonam-resistant Klebsiella oxytoca strain HB60.
Klebsiella oxytoca strain HB60 is highly resistant to cefoperazone and aztreonam (MICs = 128 mg/L). It produces a chromosomally encoded beta-lactamase of pI 5.7 which was highly efficient against penicillins, first-generation cephalosporins and cefoperazone, a non-oxyimino third-generation cephalosporin. Aztreonam and oxyimino broad-spectrum cephalosporins were less good substrates. The beta-lactamase activity was susceptible to inhibition by clavulanic acid (IC50 = 1 microM). The enzyme purified to homogeneity had a specific activity towards benzylpenicillin of 3670 U/mg. The 263 amino acid residues of the protein were sequenced by Edman degradation of proteolytic peptides. The beta-lactamase was shown to belong to the OXY-2 group as it had only one amino acid substitution (Asn for Asp at ABL position 197) compared with the beta-lactamase (pI 5.2) from the aztreonam-susceptible K. oxytoca strain SL911 and two substitutions (Ala223 for Val and Asp255 for Asn) compared with the beta-lactamase (pI 6.4) from the aztreonam-resistant K. oxytoca strain D488. These three OXY-2-group enzymes behave in the same way towards beta-lactam antibiotics. The variability in the resistance of these K. oxytoca strains would thus seem to be due to variation in the level of production of the beta-lactamases rather than to structural alteration of the enzymes.
Farzaneh
S
S
Laboratoire de Chimie, URA 401, IFR 63 CNRS, Muséum National d'Histoire Naturelle, Paris, France.
Péduzzi
J
J
Sofer
L
L
Reynaud
A
A
Barthélémy
M
M
Labia
R
R
D000595:Amino Acid Sequence; D001398:Aztreonam / Q000494:pharmacology; D002511:Cephalosporins / Q000378:metabolism; D004352:Drug Resistance, Microbial; D007709:Klebsiella / Q000187:drug effects / Q000201:enzymology*; D008969:Molecular Sequence Data; D008997:Monobactams / Q000494:pharmacology; D010406:Penicillins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D001618:beta-Lactamases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism
D002511:Cephalosporins; D008997:Monobactams; D010406:Penicillins; D001618:beta-Lactamases; D001398:Aztreonam